.flex{
    display: flex;
}
.flex_center{
    display: flex;
    justify-content: center;
}
.flex_center_center{
    display: flex;
    justify-content: center;
    align-items: center;
}
.flex_start_center{
    display: flex;
    justify-content: flex-start;
    align-items: center;
}
.flex_end_center{
    display: flex;
    justify-content: flex-end;
    align-items: center;
}
.flex_between_center{
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.flex_between_baseline{
    display: flex;
    justify-content: space-between;
    align-items: baseline;
}
.flex_around_center{
    display: flex;
    justify-content: space-around;
    align-items: center;
}
.flex_around_start{
    display: flex;
    justify-content: space-around;
    align-items: flex-start;
}
.flex_end_center{
    display: flex;
    justify-content: flex-end;
    align-items: center;
}
.flex_none_center{
    display: flex;
    align-items: center;
}
.flex_start_badeline{
    display: flex;
    justify-content: flex-start;
    align-items: baseline;
}


html{
    scroll-behavior:smooth;  //平滑滚动
}
a{
    list-style: none;
    text-decoration:none;
    color:inherit ;
}